Potable (drinking) water is commonly found in large commercial transport vehicles such as aircraft, railroad passenger cars, buses, boats and ships. Such water is placed on board these transport vehicles for use as drinking water, making ice cubes, culinary, cleaning and other sanitary purposes. Care must be taken to assure that harmful bacteria and organisms are not present and/or multiplying in the water found inside the potable water storage and distribution systems in these conveyances. Some organisms can live and multiply very rapidly under certain conditions. Most frequently cited to be of concern are coliform, E.coli, and legionella, but other common bacteria in domestic water supplies in the United States, Canada, and other countries include, but are not limited to, salmonella typhia, shingella sonnei, dysenteria, flexneri, boydii, vibro cholerae, campylobacter jejuni, yersinia enterocolitica, plesiomonas shigellojodes, and aeromonas hydrophila. Therefore, care is needed in the treatment and handling of water intended for such uses.
Within the United States, the Environmental Protection Agency has a responsibility for regulatory enforcement of the Safe Water Drinking Act of 1974. The Act covers, among other things, municipal drinking water supplies and other water supplies being used by the public. Other politically stable and economically developed countries have similar agencies with similar responsibilities. It is recognized by these agencies that it is economically impossible to provide absolutely pure water. There are, however, achievable, appropriate, and economical limits to the concentration of chemical, mineral, and organic contaminants. These contaminant concentrations are very low and generally do not represent a health threat to the general population.
Most of the watering points used to transfer water into the transport are filled using municipal, and otherwise regulated, treated public water supplies. Acceptably low concentrations of some offensive organisms are routinely introduced into watering points and consequently could find their way into the transport's potable water storage tank(s). Given the right conditions, these offensive organisms can grow and multiply and develop higher concentrations that can be harmful to otherwise strong and healthy people. These organisms can also form biofilms within watering points and a transport's potable water storage tank(s). Such biofilms can re-contaminate watering points and the transport's potable water storage tank(s) even after they have been emptied, flushed, and refilled.
One method for filling a storage tank(s) in a transport's potable water system is the utilization of a potable water station which may take the form of a potable water cabinet (PWC). The PWC is essentially a cabinet containing piping, hose, hose reels, and other components compatible with drinking water that are used to convey water from the water supply into the transport's potable water storage tank(s).
The conventional method of cleaning the PWC's relates to the EPA's recommended procedure for the sterilization of watering points which generally conforms to the following description:
1. Prepare the chlorine solution at a concentration of 5.25% chlorine bleach having no additives. It is best to prepare a volume more than the internal volume of the water point.
2. Pump the solution into the piping of the watering point in a rapid, continuous flow.
3. Continue pumping until the odor of the chlorine is detected at the discharge nozzle.
4. Attach the discharge nozzle to the suction side of the pump used to fill the watering point and recirculate the chlorinated water within the watering point for at least one hour.
5. Stop the pump and allow the chlorine solution to remain within the plumbing of the watering point for at least 1 to 4 hours. Flush the entire system until it is free of chlorine and dispose of the chlorinated water in compliance with hazardous waste rules.
6. This process may be repeated. For some difficult infestations a higher concentration of chlorine or use of hot water or steam may be required to disperse slime and kill bacteria.
Difficulties have been encountered using this method due to: the complexities of transporting and mixing chemicals; the requirements with respect to safety goggles, safety aprons; gloves, etc. (in compliance with OSHA Regulations); the total time required; the exposure time required to effectively disinfect the PWC's wetted internals (hose, valves, piping, and couplings); the post-cleaning complete flushing of the PWC's wetted internals to eliminate the chemicals; and the proper disposal of the waste of the used chemicals flushed from the system (in accord with EPA Regulations).